This invention is concerned with an apparatus to remove carbon dioxide from exhaust gas from thermal power plant efficiently with minimum energy.
There have been strenuous efforts worldwide to reduce carbon dioxide emission from industry and household, in order to cope with global warming. For this purpose, energy-consuming equipments are being developed to make them as energy efficient as possible, so as to be replaced with older models. Also, in the electricity generation, such renewable sources as solar power or wind power have been vigorously pursued, the generation efficiency of conventional fossil-fuel burning power plants has been tried to be improved, and techniques of carbon capture and storage (CCS) of exhausted carbon dioxide from fossil-fuel burning power plants to underground or ocean have been developed.
Among the items described above, the present invention is concerned with the techniques of carbon capture and storage (CCS) of exhausted carbon dioxide from fossil-fuel burning power plants to underground or ocean.
Among thermal power plant, oil, natural gas and coal are the most widely used fuels, and exhausts from urban areas are also burned. Among these, coal-burning power plants have the following features; the fuel is cheap and its world reserve is much larger than oil, and distributed rather evenly all over the world, resulting in easy access and thus stable supply of electricity.
However, carbon dioxide emission per power output for coal is larger than that for oil and natural gas, and emission of sulfurate gas is also larger. In addition, heavier components of oil have similar problems. Due to these reasons, power plants using coal and heavier components of oil have equipped with apparatus for removing sulfur oxides and nitric oxides in order to alleviate environmental pollution.
Even after removal of sulfur oxides and nitric oxides, carbon dioxide is emitted in large quantity, resulting in becoming the cause of global warning.
In order to cope with this, a technique of separating (capturing) carbon dioxide from the exhaust gas, and storing it into underground or ocean (carbon capture and storage, CCS) is vigorously pursued. For this purpose, a number of proposals have been put forward for separating carbon dioxide, and one of them is to use adsorbing agents of carbon dioxide. For this case, there is a problem of moisture in the exhaust gas which prevents the adsorption process of carbon dioxide.
In other words, exhaust gas contains moisture which results from chemical reactions of hydrogen molecules in the fuel, nitric and sulfur oxides which result from chemical reactions of nitrogen and sulfur, all with oxygen molecules in air during the burning process. While nitric oxides are dissociated by catalytic actions at the ammonia contact reduction method and sulfur oxides are removed by using the wet caustic lime in which fluids containing caustic lime are sprayed into the exhaust gas.
For this reason, it is apparent of the problem caused by the presence of a large amount of moisture in the exhaust gas which prevents the adsorption process of carbon dioxide by adsorbing agents such as zeolite. In order to cope with this, a technique of removing moisture from the exhaust gas has been developed, as disclosed in the patent document 1.
[Precedents]
[Patent Documents]
[Patent Document 1] Japan 2009-242160
[Patent Document 2] Japan 2004-344703